The best CO detectors, compared.
Top pick: XINDUM CO08 Best value: FireAngel FA6813 – About £13.98 with both dated standards, replaceable AA cells and 4.7 from 8,616 reviews, and the listing excludes Scottish homes. Updated October 2026.
The NHS lists headache, dizziness, nausea and confusion, and those symptoms can ease once you are outdoors. A CO detector warns you when gas from a boiler, fire or stove reaches a hazardous level. Its listing says it is not for Scottish homes. The checks behind that split are in the [CO detector buying guide](/hub/fire-protection/co-detector/sub/co-detector-buying-guide). It is not a smoke alarm, and it is not a carbon dioxide monitor. If the alarm sounds, or people have those symptoms, get out, stop the appliance, and get medical help. Do not reuse the appliance until a competent person has checked it.
The NHS lists headache, dizziness, nausea and confusion, and those symptoms can ease once you are outdoors. A CO detector warns you when gas from a boiler, fire or stove reaches a hazardous level.
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Personal buying guide
Question 1 of 2
Where will you fit the alarm?
The CO08 lists a display from 10 to 999 ppm, two alkaline AA cells claimed for one year, a 10-year sensor and 85 dB, at about £14.15. The star line is 4.9 from 52 ratings, and the saved listing holds 41 UK reviews, all read. Longer notes like the live readout, the green flash, and the warning above 20 ppm that stays below alarm level for over 35 minutes, with one beep every three minutes. Batteries are already fitted, and reviewers mention travel, a camper van, or a replacement for an expired seven-year alarm. Several lines are short notes, and some reviewers call it a CO2 or carbon dioxide detector. There is no repeated hardware failure in those 41 reviews. EN 50291 and CE are named with no year and no Kitemark, and the compatible-devices line says Incompatible. A 4.9 on 52 ratings is a thin sample, and the cells are a one-year claim.
Pros
Cons
Best for: Travel or a camper van where you want a number on the screen and you will replace the AA cells on the one-year claim.
Less suitable: A main home alarm that needs a large review file or a sealed 10-year cell.
Specifications
Common questions
How long do the AA cells last?
The listing says a 1-year battery lifespan and a 10-year sensor. Two alkaline AA batteries are included.
What is the 20 ppm warning?
If CO stays above 20 ppm and below the minimum alarm sensitivity for over 35 minutes, the listing says one red flash and one beep every 3 minutes.
How many reviews are there?
The listing shows 4.9 from 52 ratings. The saved listing contains 41 UK review texts.
The PG-C11 one-pack is listed at about £14.27 with a real-time CO display, replaceable AA cells, a silent test button and an 85 dB claim. The amazon.co.uk line is 4.8 from 137 reviews, and that pool is shared with the two-pack, so this listing has no separate evidence. In the first 50 UK reviews, buyers like the compact body, the number on the screen, and fitting with batteries, screws, a wall plate or a sticky pad, including taking it on holiday. Several cannot say whether it would alarm for CO over time. The spec line says photoelectric on a product sold as a carbon monoxide alarm, and the compatible-devices line says smartphone even though the bullets do not describe an app. No standard number is on the listing, and one review about a pair may belong to the two-pack. There is no repeated early-death cluster in those 50 reviews.
Pros
Cons
Best for: A single travel display if you accept a shared review file and a photoelectric spec line.
Less suitable: A household alarm that needs its own reviews and a named electrochemical standard.
Specifications
Common questions
Is a British Standard named?
No. The listing does not print BS EN 50291.
Why does the sensor say photoelectric?
That is the spec line. The bullets describe a carbon monoxide alarm and do not explain the word. The conflict is left as printed.
Are the 137 reviews only for this one-pack?
No. The same count, rank and review texts appear on the two-pack listing.
The two-pack lists two PG-C11 alarms at about £25.98, with the same display, replaceable AA cells, silent test and 85 dB claim as the one-pack. The star line is again 4.8 from 137 reviews, the same pool, so these notes are shared evidence rather than a separate two-pack record. One reviewer says two alarms sit on shelves in a bungalow. Buyers still cannot say whether the unit would alarm for CO, and the shared notes do not describe a fault that belongs only to this pack. The spec line says photoelectric. Dimensions are printed as a 10 x 10 x 10 cm cube at 150 g, while the one-pack spec is 3.4 x 7.2 x 12.6 cm. No standard number is named. You pay about £25.98 for two units whose reviews are the one-pack file, with a sensor line that reads photoelectric.
Pros
Cons
Best for: Two rooms in one order if you already accept the shared 137-review file and the photoelectric line.
Less suitable: Anyone who wants a separate review file, a named standard, or the cheaper single unit.
Specifications
Common questions
Is this a different alarm from the one-pack?
The model number is the same PG-C11. This listing is the 2-piece pack at about £25.98.
Do the reviews belong only to the pair?
The saved listing repeats the one-pack's 137 reviews, rank and texts. One review mentions two alarms on shelves.
Is a standard printed?
No BS EN 50291 line is on this listing.
The 5CO is a battery carbon monoxide alarm at about £13.75 with a 10-year sensor claim, an end-of-life alert and a test/reset, and it carries 4.7 from 59,540 amazon.co.uk reviews, the largest file in this set. In the first 50 UK reviews, people fit it with screws and plugs or stand it on a shelf, call the test beep loud, and say two AA batteries are included. One buyer replaced a detector about nine years old and says the new unit fitted the old plate. There is no repeated failure or false-alarm cluster in those 50 reviews, and several notes are one line from people who have not had a real CO event. The listing has no standard number, and the spec line says photoelectric on a product the page also warns is not a smoke alarm. That conflict is why the score is 58 beside a review count this large. A 7-year warranty is stated. You are buying the most reviewed alarm here, with a sensor line that reads photoelectric.
Pros
Cons
Best for: A compact wall or shelf alarm where the size of the review file matters and you will check the sensor line on the page.
Less suitable: Anyone who needs a named electrochemical sensor and a dated BS EN 50291 claim.
Specifications
Common questions
Does the Kidde 5CO state BS EN 50291?
No. The captured listing has no standard number.
Are the batteries replaceable?
The listing does not say. Reviews mention two included AA batteries. The title claims a 10-year sensor, not a sealed cell.
Is it a smoke alarm?
The listing warns that this CO alarm is not a substitute for a smoke or fire alarm. The spec line still says photoelectric.
The FA6813 is an electrochemical alarm at about £13.98 with two replaceable AA cells, 85 dB(A) at 3 metres, and the listing names BS EN 50291-1:2008 and EN 50291-2:2019. Across 8,616 amazon.co.uk reviews at 4.7, people hang it near a boiler or use the screws in a caravan, and several bought it to replace an expired FireAngel, including units associated with British Gas. Reviewers treat the replaceable cells as an improvement on an older sealed FireAngel that died after seven years. Sleep Easy mutes the low-battery chirp for eight hours while the amber light keeps flashing. There is no ppm screen. The new housing does not match older FireAngel screw spacing, so one old hole could not be reused. The listing says it suits homes in England and Wales, and not Scottish homes under the new regulations. It is the best value here, with both dated standards and a large review file at about £13.98.
Pros
Cons
Best for: An English or Welsh home, or a caravan, where you want dated standards and batteries you can replace.
Less suitable: A Scottish home under the rules the listing excludes, or anyone who wants a sealed 10-year cell and a Kitemark.
Specifications
Common questions
Can I use the FA6813 in a Scottish home?
The listing says it is suitable for homes in England and Wales, but not for Scottish homes under the new regulations.
Does the low-battery chirp silence?
Yes. Sleep Easy mutes the low-battery chirp for 8 hours. The amber light keeps flashing. That is the low-battery mute, not a CO alarm mute in the listing text.
Does it include a screen?
No ppm display is listed. The alarm pattern is four chirps and a flashing red CO light.
The 7DCOC keeps a continuous CO reading on the screen and runs on three replaceable AA cells, listed at about £18.25 with a 10-year end-of-life alert. Across 6,393 amazon.co.uk reviews at 4.7, including notes from 2015 and 2018 as well as 2026, buyers praise the loud test, the simple battery insert, and a previous unit that lasted about 10 or 11 years until end of life. One review uses the same fixing footprint in a motorhome. The listing does not name a standard or a decibel figure. The spec line prints a width of 48.3 cm and the material Carbon, which a 2015 review contradicts by calling the unit about the size of a cigarette packet. One recent review reports a low-battery alarm after less than a month, at night. The warranty line is printed as warraty. You get a long-running display alarm with a large review file, and the page does not print a BS EN number.
Pros
Cons
Best for: A home or motorhome where you want a continuous reading and batteries you can change, without relying on a standard line the listing omits.
Less suitable: Anyone who needs BS EN 50291 printed on the listing, or who wants a sealed cell.
Specifications
Common questions
Does the screen stay on?
The listing says the digital display continuously shows the CO level detected.
When do I replace the unit?
The listing says an end-of-life alarm tells you to replace it after 10 years. The batteries are replaceable before that.
Does the listing name a British Standard?
No standard number is printed. It does warn that the alarm is not a smoke or fire alarm.
The XC0C-SR is listed at about £15.98 with a screen for the current CO level and peak memory, two pre-installed AA cells claimed for three years, and a 10-year sensor. Across 6,311 amazon.co.uk reviews at 4.7, buyers like the readout as a sign the unit is on, and the box includes screws, plugs and a drill-hole label. The listing says it conforms to EN 50291, with no year and no Kitemark, and it does not state a decibel figure. Once the alarm is mounted as instructed, the peak and test buttons are hard to see. At least one review in the first 50 describes an XC0C-iR smart model and an app, which this listing does not claim, so that complaint sits in the wrong pool. The colour cell says Yellow467, so check the photo before you trust that row. You get a readable display and a large review count, with buttons that are awkward after fitting and a standard line that has no year.
Pros
Cons
Best for: A wall or shelf alarm where you want a ppm screen and peak memory, and you can still reach the buttons after fitting.
Less suitable: Anyone who needs a dated BS EN number, a stated sound level, or an app, which this listing does not claim.
Specifications
Common questions
How long do the batteries last?
The listing says replaceable AA batteries that last 3 years, and a 10-year sensor. They are pre-installed.
Can it stand on a shelf?
Yes. The listing also includes screws and plugs for a wall.
Does the listing include a decibel figure?
No. It does claim conformance to EN 50291, with no year printed.
The FA3820 is a sealed electrochemical alarm listed at about £22, with a tamper-proof 10-year cell, 85 dB(A) at 3 metres, and a BSI Kitemark to BS EN 50291-1:2018 and EN 50291-2:2019. Across 3,466 amazon.co.uk reviews at 4.6, buyers fit it with the screws, including above a wood-burning stove, and several bought it on a chimney sweep's advice. The sealed cell means there are no batteries to change, and reviewers also call it small enough to take when travelling. One clear report describes a fault at about two years, and because the cell is sealed you replace the whole unit. The status flash is called dimmer than an older FireAngel CO-9X, and the screw spacing does not match a previous FireAngel, so a replacement can need new holes. Most of the first 50 reviews have not seen a real CO event, so detection is unproven in those notes. It is the top pick in this set: the only listing that prints the Kitemark, the sealed 10-year cell, and both of those standard years.
Pros
Cons
Best for: A domestic or rental home where you want a Kitemarked sealed alarm and you can replace the whole unit if it fails early.
Less suitable: Anyone who wants to swap AA cells, or who is replacing an older FireAngel and expects the old screw holes to line up.
Specifications
Common questions
Can I change the battery?
No. The listing says the 10-year battery is sealed and tamper-proof. One review says the unit faulted after two years and the cell could not be changed.
Which standard does the listing name?
UKCA, a BSI Kitemark, and third-party approval to BS EN 50291-1:2018 and EN 50291-2:2019.
What is the 180 ppm note?
The listing says a high-sensitivity mode runs if the alarm predicts CO will rise to 180 ppm or above, with a prompt to ventilate.
The CO12 is a black electrochemical alarm at about £14.43 with a sealed 1,600 mAh lithium cell, an LCD, and an 85 dB claim. Across 1,249 amazon.co.uk reviews at 4.6, people praise the sealed cell, the ppm screen, and fitting by tape, screws or standing, including a motorhome replacement for a British Gas detector. The bullets say EN 50291 and CE, with no year and no Kitemark, and they do not give dimensions. Several reviewers call it a CO2 detector even though the listing is a carbon monoxide alarm, which is a labelling muddle rather than a repeated hardware fault. One buyer finds it expensive for something hidden by the boiler and has not seen it alarm. The first 50 reviews do not show a repeated early failure. A sealed screen unit is the practical case if you read the page as CO, and you accept an undated standard.
Pros
Cons
Best for: A freestanding or taped alarm with a sealed cell and a number on the screen, including a motorhome if you accept the missing EN 50291-2 year.
Less suitable: Anyone who needs a Kitemark, a dated standard, or review language that keeps CO and CO2 apart.
Specifications
Common questions
Is the battery sealed?
Yes. The listing says a 1600 mAh lithium battery is sealed in, with a 10-year claim.
Does it name a Kitemark?
No. It says EN 50291 and CE. No year and no Kitemark are printed.
How can I mount it?
The listing says freestanding, double-sided tape, or screws, with a bracket so it can be lifted off.
The Fenary s07 is listed at about £9.99 with an electrochemical sensor, an 85 dB claim, and three AAA cells that the title says are not included. Across 907 amazon.co.uk reviews at 4.6, people call it neat beside a gas fire, loud on test for some buyers, and useful as a spare or for cooking in a camper. A green flash every 30 seconds is the idle sign once you know to look for it. The screen stays blank in normal use until you press the button, although the bullet says you can see the ppm value when the detector is in alarm. One buyer bought another alarm because this one did not seem to meet a British Standard, and the listing does not name BS EN 50291. Buyers also call it a CO2 detector. The spec line prints 40 x 40 x 5 mm beside a bullet of 123 x 70 x 25 mm. One review says the first batteries set the alarm off and had to be replaced.
Pros
Cons
Best for: A spare or holiday alarm where a button-press reading is enough and you will supply the AAA cells.
Less suitable: Anyone who wants a live idle ppm figure or a named British Standard on the listing.
Specifications
Common questions
Does the screen show a live reading?
The bullet says the ppm lights go out with no operation and a green LED flashes every 30 seconds. Reviews say you press the button to see a reading.
Are batteries included?
The title says batteries are not included. The listing says three AAA cells.
Which size is printed?
The bullet says 123 × 70 × 25 mm. The spec line says 40 × 40 × 5 mm. Both are kept.
The BDC-CO305B is an electrochemical screen alarm at about £9.99 that claims 85 dB and an immediate alarm at 100 ppm, and the bullet says it has passed EN 50291 with no year and no Kitemark. Across 1,013 amazon.co.uk reviews at 4.3, people use it for travel, caravans and holiday lets, and some like a screen that shows 0 ppm at home. The title says the ppm value stays visible, after a 30-second countdown. Reviews say the three AAA cells were not in the parcel, and a deep screw is the back plate rather than the battery door, which confused at least one reader. One buyer says the unit stopped after about four weeks. Another finds it not very loud and is not convinced by informal tests. The immediate 100 ppm line is a listing claim, not a timed response curve. It is a low-priced screen for a garage or a trip if you supply the cells and weigh that four-week report.
Pros
Cons
Best for: A low-cost spare for a holiday let, caravan or garage once you have three AAA cells.
Less suitable: A main household alarm, given missing batteries and one report of failure at about four weeks.
Specifications
Common questions
Are batteries in the box?
The included-components line lists only the detector. Reviews say the AAA cells were not included.
When does the listing say it alarms?
It says the alarm activates immediately when carbon monoxide reaches 100 ppm, with a red LED and an 85 dB sound.
Did reviews report failures?
One review says it stopped after four weeks. Another says it is not very loud. Others use it for travel.
The AW-D125S is listed at about £3.42, with an LCD, an 85 dB claim, and a bullet that says the alarm activates immediately at 100 ppm. Across 290 amazon.co.uk reviews at 4.1, some buyers like the small body and the loud test, and one says it alarmed when a motorbike started in the garage. Several reviews say the AA cells lasted about a week, or needed two changes in a short time, even when a gauge still showed the cells as good. Rechargeable AA cells lasted just over a week in one side-by-side comment, while alkaline lasted longer. A beep every minute, and units that did not last, come up as well. The listing claims standby of about 10 months, which those reviews do not match, and a blank screen means the cells are exhausted. EN 50291 is named with no year. At this price the screen is one that several reviewers could not keep powered.
Pros
Cons
Best for: A very cheap check beside a garage or a camping trip if you keep spare alkaline AA cells to hand.
Less suitable: A fitted home alarm, or rechargeable cells, given the week-long life in several reviews.
Specifications
Common questions
How long did batteries last in reviews?
Several reviews say about a week, or two changes in a short time. One says rechargeable cells failed sooner than alkaline. The bullet claims about 10 months standby.
When does the listing say it alarms?
Immediately at 100 ppm, with a red LED and 85 dB. A short press can turn the sound off.
What is the price in this capture?
About £3.42 on the amazon.co.uk listing captured on 19 October 2026, with 4.1 from 290 ratings.
This page compares 12 carbon monoxide alarms from amazon.co.uk listings captured on 19 October 2026. The score runs from 0 to 100: stars out of 25, the size of the review file out of 20, the standard and sensor line out of 30, and household fit out of 25. A 4.7 star line does not repair a missing standard or a photoelectric spec line on a product sold as a CO alarm. There is no lab test.
Standard and sensor
30%A dated BS EN 50291 claim and an electrochemical sensor score higher than an undated EN line. A missing standard, or a photoelectric spec line on a CO alarm, scores low. Only the FireAngel FA3820 prints a BSI Kitemark in this set.
Household fit
25%Sealed life batteries, end-of-life warnings, a stated sound level and a battery that matches the nation score higher. Replaceable cells, a Scotland exclusion on the listing, or cells that reviews say die within weeks score lower.
Stars
25%The amazon.co.uk star rating is mapped to 25 points. It is one part of the score, not the rank on its own.
Review sample
20%Larger amazon.co.uk review files score higher. The two FUMIXTEX packs share one pool of 137 reviews, so neither receives a second sample.
Judge a CO detector by the gas it names, a BS EN 50291 claim, and a battery that matches the nation. Stars and the review count come after that. The notes below are the same checks used to score the 12 amazon.co.uk listings on this page. There is no lab result behind them.
A carbon monoxide detector is a battery alarm that sounds when CO from a boiler, fire or stove reaches a hazardous level. It is not a smoke alarm, and it is not a carbon dioxide monitor. The NHS says the gas has no smell, and that headache, dizziness, nausea and confusion can ease once you are outdoors. If the alarm sounds, or people have those symptoms, get out, stop the appliance, and get medical help. Do not reuse the appliance until a competent person has checked it.
Carbon monoxide, carbon dioxide and smoke are different jobs. Kidde prints that a CO alarm is not a smoke alarm. Reviewers still call some XINDUM and EiBEST units CO2 detectors. Read the gas on the listing before you fit it.
Both EiBEST listings claim an immediate alarm at 100 ppm. FireAngel's EN 50291 times are 50 ppm in 60 to 90 minutes, 100 ppm in 10 to 40 minutes, and 300 ppm or more within 3 minutes. The immediate line is a listing claim, not that curve.
Scotland expects a life-of-detector battery or hard-wired mains. The FA6813 listing says it is not for Scottish homes. A sealed cell is not automatically enough: the FA3820 prints a Kitemark, and the XINDUM CO12 does not.
Start with the gas. A CO detector is for carbon monoxide from a boiler, fire or stove. It is not a carbon dioxide monitor and it is not a smoke alarm. Then look for a BS EN 50291-1 claim with a year. For a caravan, also look for EN 50291-2. In these 12 listings only the FireAngel FA3820 prints a BSI Kitemark, and it names BS EN 50291-1:2018 and EN 50291-2:2019. The FireAngel FA6813 names both parts with years, but part 1 is still the 2008 year and there is no Kitemark.
Match the battery to the nation, not to the cheapest pack. Scotland expects a life-of-detector battery, or hard-wired mains with a sensor-failure warning. English landlord rules do not stipulate the type. GOV.UK recommends a sealed cell if you choose a battery. Approved Document J, when you install a qualifying appliance in England, expects a life battery with an end-of-life warning, or fixed mains with a sensor-failure warning.
Three typical situations, each with a recommendation from this comparison.
You want a life battery you do not change, and a listing that prints a Kitemark. The FireAngel FA3820 is the only alarm here with a sealed 10-year cell, a BSI Kitemark, and both BS EN 50291-1:2018 and EN 50291-2:2019. If it faults early, you replace the whole unit.
You can change AA cells and you want dated standards at a lower price. The FireAngel FA6813 names BS EN 50291-1:2008 and EN 50291-2:2019, includes two AA cells, and the listing says it suits England and Wales, not Scottish homes.
You want a number, not only a siren. The X-Sense XC0C-SR shows the current CO level and peak memory, with replaceable AA cells claimed for three years. The EN 50291 line has no year and no Kitemark, and the buttons are hard to see once it is mounted.
The FireAngel FA3820 leads this set because it is the only listing with a BSI Kitemark, a sealed 10-year cell, and both BS EN 50291-1:2018 and EN 50291-2:2019. One review describes a fault at about two years, and the sealed cell means you replace the whole unit. The FireAngel FA6813 is the best value at about £13.98, with both dated standards and 8,616 reviews, and the listing says it is not for Scottish homes. The Kidde 5CO has the largest review file, but it names no standard and the spec line says photoelectric.
FireAngel FA6813
About £13.98 with both dated standards, replaceable AA cells and 4.7 from 8,616 reviews, and the listing excludes Scottish homes.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources and the FireAngel FAQ, last checked on 19 October 2026.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are the 19 October 2026 listings. We did not run a lab test.
